Search PubMed⌕ Search

Biomedical subjects

J D Spence

Publications and source records attributed to J D Spence.

117 records · Page 7Linked to original sources
PubMedDate not supplied

Carotid endarterectomy does not affect long-term blood pressure: observations from the NASCET. North American Symptomatic Carotid Endarterectomy Trial.

The aim of the study was to examine how blood pressure is affected by carotid endarterectomy over a 2-year period. We analyzed the data from 997 patients who received best medical care alone and 999 patients who received best medical care plus carotid endarterectomy (CE). All patients were recruited by the North American Symptomatic Carotid Endarterectomy Trial and were followed at regular clinic visits. The mean blood pressure at baseline was 145.2/81.2 mm Hg for medically treated patients and 146.2/81.9 mm Hg for surgically treated patients. The mean systolic and diastolic pressures increased by approximately 2.5% in the first month following randomization, then decreased over the next year and then remained relatively uniform. Throughout follow-up, surgical patients had slightly higher blood pressures than medically treated patients. At the end of 2 years, the mean systolic pressures in the two treatment groups converged to 147.6 mm Hg. The mean diastolic pressure in the medical patients returned to its baseline value, whereas the surgical patients' blood pressure remained slightly elevated by 0.5 mm Hg. The percentage of patients on antihypertensive medications mirrored the rise and fall in blood pressures. A sharp decrease in medication (from 56 to 43%) was observed in both treatment groups at 1 month. The percentage of patients on medication increased subsequently, with approximately 63% taking medication at the end of 2 years. CE does not affect long-term blood pressure. The use of antihypertensive medications appears to be the key component in blood pressure management. As hypertension is related to neurologic morbidity and mortality, strict regulation of blood pressure is extremely important in patients with cerebrovascular disease.

Aged↗
PubMedDate not supplied

Management of resistant hypertension in patients with carotid stenosis: high prevalence of renovascular hypertension.

INTRODUCTION: Patients with carotid stenosis are at high risk of vascular events and therefore require an optimal control of risk factors such as hypertension. As the treatment of hypertension differs according to the cause, we examined the prevalence of resistant hypertension, and the cause of hypertension, among patients with carotid stenosis followed closely in two randomized trials of carotid endarterectomy. OBJECTIVE: The purpose of this study was to determine the prevalence of resistant hypertension and of secondary hypertension among patients with carotid stenosis. METHODS: A chart review was performed of all patients from our center who participated in the North American Symptomatic Carotid Endarterectomy Trial or the Asymptomatic Carotid Artery Study to determine the prevalence of renovascular hypertension. RESULTS: Among 170 patients with carotid stenosis followed in these two trials, 145 (83.5%) were hypertensive (systolic >160 or diastolic >90 mm Hg); at least 24 (14.1% overall, 16.6% of hypertensives) had renovascular hypertension based on either nuclear medicine renography, renal angiography or both; among the 79 patients with resistant hypertension (mean arterial pressure >130 mm Hg despite treatment), 20 (25.3%) had renovascular hypertension. Adrenocortical hyperplasia was the underlying cause of hypertension in 12 (7.1% of cases, 8.3% of hypertensives, 8.8% of resistant hypertensives). Blood pressures were significantly higher for patients with renovascular and adrenocortical hypertension (p < 0.0001 for systolic, p = 0.024 for diastolic pressures). CONCLUSION: Among patients with carotid stenosis, renovascular hypertension is unusually common. Resistant hypertension among such patients should lead to investigation and management directed at the cause of hypertension. Appropriate investigations might include plasma renin/aldosterone ratio, captopril renography and MRA of the renal arteries or renal angiography.

Aged↗
PubMedDate not supplied

Hemodynamic effects of antihypertensive drugs. Possible implications for the prevention of atherosclerosis.

By lowering blood pressure, a number of hypertensive complications can be prevented, including congestive heart failure and such consequences of hypertensive arteriolar disease as nephropathy, intracerebral hemorrhage, and lacunar stroke. Whether atherosclerotic complications such as myocardial infarction can be prevented is more problematic and may depend on effects of the antihypertensive drugs other than the reduction of blood pressure, such as effects on plasma lipids and possibly hemodynamic effects. The following discussion summarizes a series of studies that suggest that the hemodynamic effects of antihypertensive drugs may be an important aspect of this problem. In studies in rhesus monkeys and hypertensive patients, antihypertensive drugs were shown to have differing effects on blood velocity and heart rate, important parameters in the genesis of arterial flow disturbances. In patients with carotid stenosis, hydralazine increased, whereas propranolol reduced, the occurrence of abnormal high-velocity flow patterns associated with turbulence and vortex formation. In a hypertensive (one kidney, one-clip) cholesterol-fed rabbit model, propranolol was significantly more effective than hydralazine in preventing the occurrence of aortic atherosclerosis. These observations suggest that the cardioprotective effect of beta blockers may extend to an antiatherosclerotic effect by hemodynamic mechanisms. This hypothesis is being further tested in patients with carotid stenosis.

Animals↗
PubMedDate not supplied

Problems in design of stroke treatment trials.

Critical evaluation of the literature was use to identify remediable flaws in the design of clinical trials of stroke treatment. Trials of dexamethasone, dextran, and glycerol were reviewed. Available studies have in common major weaknesses in case selection (failure to exclude arteriolar strokes due to hemorrhage or lacunar infarction), and failure to estimate required sample size. Problems of case selection can be avoided with computerized tomography; the sample size required to show superiority of active treatment over placebo can be estimated using standard formulas. Prognostic stratification is suggested as a method of overcoming problems of unbalanced allocation. Further studies with improved design are required to evaluate the prospects for medical limitation of cerebral infarct size.

Adult↗
PubMedDate not supplied

Effects of antihypertensive drugs on blood velocity in rhesus monkeys.

Increasing evidence suggests that higher blood velocity, by causing turbulence and high shear rates at the endothelial surfaces of arteries, may be important in the pathogenesis of atherosclerosis. In order to measure the effects of antihypertensive agents on blood velocity, an improved method has been developed for analysis of Doppler ultrasound velocity recordings. The audio signal from a Doppler velocity meter is subjected to spectral analysis; the sonagraph thus obtained is digitized with the use of a magnetic table on-line with a calculator. Four monkeys were maintained at a hypertensive baseline for six weeks by infusion of angiotensin and isoproterenol. The effects on blood velocity of 72-hour infusions of propranolol, clonidine, hydralazine, and methyldopa were studied. In doses that reduced diastolic pressure by 13--28%, propranolol decreased mean blood velocity (mv) by 17%, clonidine decreased mv by 14%, while methyldopa increased mv 12%, and hydralazine increased mv by 52% (p less than .00001). Antihypertensive drugs appear to have different effects on blood velocity; these differences may influence choice of antihypertensive drugs for the prevention of arterial disease.

Animals↗
PubMedDate not supplied

Discrepancies between clinic and ambulatory blood pressure responses to cilazapril therapy.

OBJECTIVE: To evaluate the antihypertensive effects of cilazapril, a new angiotensin-converting enzyme inhibitor, on clinic and ambulatory blood pressure (ABP) after first and last dose administrations. DESIGN: Four weeks randomized, double-blind, controlled trial of three regimens. SETTING: Six hypertensive research clinics in Canada. PATIENTS: After a two-week placebo run-in period, 130 patients aged 22 to 77 years with mild to moderate essential hypertension were randomized and evaluated. Exclusion criteria were secondary hypertension, childbearing potential and other significant diseases. INTERVENTION: Patients were assigned to cilazapril 2.5 mg (44 patients), cilazapril 5 mg (42) or placebo (44). Fourteen patients in each group were further evaluated in a substudy by 24 h ABP monitoring. MAIN RESULTS: Cilazapril in either dosage induced significant and similar antihypertensive effects on clinic blood pressure shortly after dosing (2 to 4 h), persisting during chronic treatment; however, no relevant effect persisted at the end of dosing (24 h). After four weeks, at the end of dosing, 22, 24 and 38% of patients were clinical responders (decrease in sitting diastolic blood pressure 10 mmHg or greater) on placebo, 2.5 or 5 mg (differences not significant). Conversely, both cilazapril regimens induced similar and significant (P < 0.01) falls in mean 24 h ABP compared with placebo. Moreover, 7, 50 and 48% of patients exhibited a reduction in mean 24 h diastolic blood pressure 10 mmHg or greater on placebo, cilazapril 2.5 or 5 mg, respectively. Furthermore, both regimens induced adequate trough:peak ratios on ABP.

Adult↗